Chocolate Production: A Microbial Prospective

Monday, April 27th, 2020
Finished SERO chocolate product

By: Emily Campbell

On our recent trip to Guatemala we had the opportunity to tour the chocolate production facility of SERO chocolate. They are a Guatemalan chocolate producer that integrates social and environmental responsibility with the quality cacao necessary to create fine chocolates. Their philosophy helps them create a comprehensive and quality product that connects them with people the supply chain depends on and helps expand their cultural horizons.

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The production of a finished bar of chocolate takes the input of many people and, something you may not realize - microorganisms. Chocolate’s unique flavors come from growing conditions and fermentation of the cocoa bean. Beneficial microorganisms help give chocolate its flavor, but if not controlled, harmful microorganisms can cause issues with quality and safety.

Chocolate production starts with harvesting of the mature cacao fruit by hand. The selected fruits are cut open and the beans are removed. After husking, the beans are fermented. Proper fermentation is essential for production of good tasting chocolate. Cocoa fermentation occurs naturally from the microorganisms present on healthy fruit, knives, and other surfaces the beans come in contact with. Proper conditions must be maintained on these surfaces to support growth of the beneficial microbes. The fermentation process is carried out by successive microbial populations. In the beginning yeasts dominate, then lactic acid bacteria, and finally, acetic acid bacteria dominate the population. If left to ferment for too long, spore forming bacteria, such as Bacillus, and molds can take over. Spore former growth leads to production of off flavors in the chocolate. Mold can negatively impact the flavor and safety. Some mold strains can produce mycotoxins, a harmful compound. Good storage practices below 8% humidity can prevent mold growth (1). The manufacturing process can also lower the toxin present in the sample by removing the husk from the bean (2). The color of the beans is used to determine the degree of fermentation. Once completed, the fermented beans are then dried which reduces bitterness, astringency, and acidity. It also reduces the moisture content to levels that are safe for storage and transport. If moisture is too high mold growth can spoil or contaminate the product. The beans are then processed into chocolate.

Cocoa nibs at the SERO chocolate production facility

The beans are cleaned to remove sand, stones and metal. The husks are removed, and the beans are roasted. The roasting process transforms the aroma precursors that originated in fermentation and drying processes into the final flavor of the chocolate. Roasting is also the critical control point in chocolate making. Critical control points are essential processes that are controlled to eliminate or reduce food safety hazards. The temperature and duration of the roasting must be long enough to inactivate biological pathogens and bring out flavors in the bean. The cocoa is then ground and fat is recovered from the beans. The resulting cocoa liquor or paste is homogenized and then cooled. The cocoa liquor is pressed, and cocoa butter is extracted. The pressed cake is pulverized and turned into cocoa powder. The final product is made by grinding cocoa liquor, sugar and cocoa butter together in a process called conching. The chocolate is stirred at a warm temperature for several hours. The stirring helps develop flavor, darken color, and stabilize viscosity. The chocolate is then tempered to create a stable crystalline structure that gives it a nice shine and stability.

Conching at SERO chocolate processing facility

There are three characteristics of chocolate that are important to maintain microbial safety of the chocolate: low water activity, high proportion of fats and sugars and pH around 5.5. These conditions limit the growth of bacteria but do not eliminate them. The pathogenic organisms of concern are Salmonella, but the likelihood of acquiring salmonellosis from chocolate is low. Salmonella could be introduced into the product through workers handling the beans. The low pH and the low water activity prevent Salmonella from growing, but this pathogen can survive in the chocolate. The roasting stage is the only step that can eliminate the pathogen from the product and is therefore a critical step in safe chocolate production.

The process of making chocolate is complex and requires several steps to bring out the characteristic flavors. Microorganisms play a big role in flavor production, but they need to be controlled to keep the product delicious and safe.

Finished SERO chocolate product

Find out more at:

  1. Agell O, Rodr ́ıguez MC, Rodr ́ıguez JJ. 2013. La seguridad alimentaria delchocolate. Available from:
  2. Copetti MV, Iamanaka BT, Frisvad JC, Pereira JL, Taniwaki MH. 2011.Mycobiota of cocoa: from farm to chocolate. Food Microbiol28(8):1499–1504.

Emily CampbellEmily Campbell

Graduate Research Assistant
Food Science and Technology






Posted In:
April 27, 2020 - 11:26am --

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